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Dear list member, the next research seminar of The Open University Statistics Group will be held on Friday, June 17th at the following venue: Alan Turing Building (room: M306), Walton Hall campus, Milton Keynes (MK7 6AA). The meeting will begin at 11 a.m., with tea and coffee available from 10.30 a.m., and usually finishes at approximately 12 noon. The meeting is free and open to all. Professor Jane Hutton (Department of Statistics, The University of Warwick) will be speaking on the topic of: “Modelling longitudinal data with bounded responses, with missing data”. Abstract: Health care interventions which use quality of life or health scores often provide data which are skewed and bounded. The scores are typically formed by adding up numerical responses to a number of questions. Different questions might have different weights, but the scores will be bounded, and are often scaled to the range 0 to 100. If improvement in health over time is measured, scores will tend to cluster near the 'healthy' or 'good' boundary as time progresses, leading to a skew distribution. Further, some patients will drop out as time progresses, so the scores reflect a selected population. We fit models based on the skew-normal distribution to data from a randomised controlled trial of treatments for sprained ankles, in which scores were recorded at baseline and at 1, 3 and 9 months after injury. We consider the extent to which skewness in the data can be explained by the clustering at the boundary via a comparison between a censored normal and a censored skew-normal model. As this analysis is based on the complete data only, a formula for the bias of the treatment effects due to informative drop-out is given. This allows us to assess under which conditions the conclusions drawn from the complete data might be either reinforced or reversed, when the informative drop-out process is taken into account. Kind Regards, Dr Steffen Unkel (Department of Mathematics and Statistics, The Open University) http://statistics.open.ac.uk<http://statistics.open.ac.uk/> -- The Open University is incorporated by Royal Charter (RC 000391), an exempt charity in England & Wales and a charity registered in Scotland (SC 038302). You may leave the list at any time by sending the command SIGNOFF allstat to [log in to unmask], leaving the subject line blank.